diff --git a/R/NAMESPACE b/R/NAMESPACE
index 415e5a9..6a5312a 100644
--- a/R/NAMESPACE
+++ b/R/NAMESPACE
@@ -6,6 +6,7 @@ export(add_regressor)
 export(add_seasonality)
 export(cross_validation)
 export(fit.prophet)
+export(layer_changepoints)
 export(make_future_dataframe)
 export(plot_forecast_component)
 export(predictive_samples)
diff --git a/utils b/R/R/utils.R
similarity index 71%
rename from utils
rename to R/R/utils.R
index 3390cf4..2116e91 100644
--- a/utils
+++ b/R/R/utils.R
@@ -1,15 +1,14 @@
 #' Get layers to overlay significant changepoints on prophet forecast plot.
 #'
 #' @param m Prophet model object.
-#' @param threshold Numeric, changepoints where abs(delta) >= threshold are significant. (Default 0.01)
+#' @param threshold Numeric, changepoints where abs(delta) >= threshold are
+#'  significant. (Default 0.01)
 #' @param cp_color Character, line color. (Default "red")
 #' @param cp_linetype Character or integer, line type. (Default "dashed")
 #' @param trend Logical, if FALSE, do not draw trend line. (Default TRUE)
 #' @param ... Other arguments passed on to layers.
 #'
-#' @return A list of ggplot2 layer.
-#'
-#' @import ggplot2
+#' @return A list of ggplot2 layers.
 #'
 #' @examples
 #' \dontrun{
@@ -21,12 +20,14 @@ layer_changepoints <- function(m, threshold = 0.01, cp_color = "red",
                                cp_linetype = "dashed", trend = TRUE, ...) {
   layers <- list()
   if (trend) {
-    trend_layer <- geom_line(aes_string("ds", "trend"), color = cp_color, ...)
+    trend_layer <- ggplot2::geom_line(
+      ggplot2::aes_string("ds", "trend"), color = cp_color, ...)
     layers <- append(layers, trend_layer)
   }
   signif_changepoints <- m$changepoints[abs(m$params$delta) >= threshold]
-  cp_layer <- geom_vline(xintercept = as.integer(signif_changepoints),
-                         color = cp_color, linetype = cp_linetype, ...)
+  cp_layer <- ggplot2::geom_vline(
+    xintercept = as.integer(signif_changepoints), color = cp_color,
+    linetype = cp_linetype, ...)
   layers <- append(layers, cp_layer)
-  layers
+  return(layers)
 }
diff --git a/R/man/layer_changepoints.Rd b/R/man/layer_changepoints.Rd
new file mode 100644
index 0000000..674c717
--- /dev/null
+++ b/R/man/layer_changepoints.Rd
@@ -0,0 +1,35 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/utils.R
+\name{layer_changepoints}
+\alias{layer_changepoints}
+\title{Get layers to overlay significant changepoints on prophet forecast plot.}
+\usage{
+layer_changepoints(m, threshold = 0.01, cp_color = "red",
+  cp_linetype = "dashed", trend = TRUE, ...)
+}
+\arguments{
+\item{m}{Prophet model object.}
+
+\item{threshold}{Numeric, changepoints where abs(delta) >= threshold are
+significant. (Default 0.01)}
+
+\item{cp_color}{Character, line color. (Default "red")}
+
+\item{cp_linetype}{Character or integer, line type. (Default "dashed")}
+
+\item{trend}{Logical, if FALSE, do not draw trend line. (Default TRUE)}
+
+\item{...}{Other arguments passed on to layers.}
+}
+\value{
+A list of ggplot2 layers.
+}
+\description{
+Get layers to overlay significant changepoints on prophet forecast plot.
+}
+\examples{
+\dontrun{
+plot(m, fcst) + layer_changepoints(m)
+}
+
+}